Abstract
The effects of weed management under coffee trees on soil physical properties were investigated during four-years experiment in Lampung, South Sumatra, Indonesia. The treatments were as follows : coffee without cover crop (clean-weeded plot); coffee with Paspalum conjugatum as cover crop (Paspalum plot) ; and coffee with natural weeds which was dominated by Clibadia surinamense (natural weeds plot). Weed management was done every two weeks by clearing all the weeds in clean-weeded plots, and cutting the weeds around the coffee trees with diameter 1 m for the weedy plots (Paspalum plot and natural weeds plot). The results showed that a better soil physical condition was achieved when the soil surface under the coffee trees was covered with Paspalum conjugatum. The average soil organic-C in the soil profile of Paspalum and natural weeds plots were 32 g/kg and 27 g/kg respectively, which were higher than in clean-weeded plot which had 20 g/kg of organic carbon. A smooth horizon boundary was found in Paspalum plot due to the abundance of its roots which was also enhancing soil color more black, and the process of wetting and drying. A strong aggregate stability was found at the Paspalum plot as indicated by penetrometer readings as well as water stable aggregate index. Two centimeters thickness of hardpan which was developed at Paspalum plot made the water movement from upper layer inhibited during the dry season. The highest porosity was found at Paspalum plot (0.64 m3m-3) followed by natural weeds plot (0.62 m3m-3) and clean-weeded plot (0.60 m3m-3). However, the average available water content was not different between Paspalum plot and natural weeds plot, and only 0.15m3m 3 higher than that of clean-weeded plot. The permeabilities varied among the treatments, and this variance was biggest in the upper layer of Paspalum plot.
